Honeycomb Structure Porosity Gradient Bonding
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Solution Overview
Problem
Existing honeycomb structures for diesel particulate filters face challenges in achieving sufficient thermal shock resistance during regeneration, leading to defects like cracks, due to the difficulty in balancing bonding strength and stress-releasing functions in the bonding material layer.
Innovation Solution
A honeycomb structure with a bonding material layer that has a specific porosity gradient, where the outside portion has a lower porosity than the central portion, and a strength-to-Young's modulus ratio greater than 1.0×10−3, combined with inorganic fibers and appropriate binder content, to enhance both bonding strength and stress-releasing capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a homogeneous bonding material layer is used to join honeycomb segments, then the bonding strength is improved, but the thermal shock resistance deteriorates due to inability to release thermal stress
Solution Approach 1:
The bonding material layer is designed with non-uniform porosity distribution, where the porosity varies in the radial direction. The outer region has higher porosity (50-80%) to provide stress-releasing function and thermal insulation, while the inner region has lower porosity (20-40%) to provide bonding strength. This local quality variation resolves the contradiction between bonding strength and thermal shock resistance.
Solution Approach 2:
The bonding material layer is formed as a composite structure with different porosity zones. The multi-layered porosity structure creates a gradient material system that combines the advantages of high porosity (stress release, thermal insulation) and low porosity (bonding strength), effectively resolving the contradiction between these opposing requirements.
2Reliability
If the porosity of the bonding material layer is increased to improve stress-releasing function, then the thermal shock resistance is improved, but the bonding strength deteriorates
Solution Approach 1:
Different regions of the bonding material layer are assigned different porosity values according to their functional requirements. The outer region with higher porosity performs stress release and thermal insulation, while the inner region with lower porosity provides bonding strength. This spatial differentiation of porosity resolves the contradiction between stress-releasing function and bonding strength.
Solution Approach 2:
The bonding material layer is segmented into multiple porosity zones (outer high-porosity region and inner low-porosity region). This segmentation allows each zone to independently perform its specific function - the outer zone for stress release and the inner zone for bonding - thereby resolving the contradiction between these competing requirements.
3Productivity
If the filter size is enlarged to increase capacity, then the productivity is improved, but the thermal stress increases leading to more defects
Solution Approach 1:
The bonding material layer's non-uniform porosity structure provides localized thermal insulation at the outer region, reducing thermal stress concentration in larger filters. This allows filter enlargement for increased capacity while maintaining thermal shock resistance through the differentiated porosity structure.
Solution Approach 2:
The high-porosity outer region of the bonding material layer acts as a cushioning layer that absorbs and distributes thermal stress before it reaches the honeycomb segments. This beforehand cushioning effect enables larger filter sizes without proportionally increasing thermal stress and defect formation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed structure effectively inhibits crack formation during regeneration by optimizing thermal shock resistance, ensuring both strong bonding and efficient stress release, thereby extending the filter's lifespan and maintaining its structural integrity.
Implementation Method 1
A high thermal stress is generated upon this regeneration of a filter, and there arises a problem of occurrence of defects such as cracks and breakage in a honeycomb structure by the thermal stress
Implementation Method 2
porosity in an outside portion of the bonding material layer is smaller than that in a central portion
Implementation Method 3
a plurality of honeycomb segments are integrally joined with one another by means of a bonding material layer
Data Source
AI summary
There is provided a honeycomb structure 10 comprising a honeycomb segment joined body 10 having a plurality of honeycomb segments 2 integrally joined with one another at a joint face of each of the honeycomb segments by means of a bonding material layer 9 and having a plurality of cells 5 functioning as fluid passages disposed in parallel with one another in a direction of central axis. Porosity in an outside portion of the bonding material layer 9 (portion from the interface of the joint face of honeycomb segments to the point corresponding to 20% thickness of the total bonding material layer) is smaller than that in the central portion located on the inner side of the outside portion.